diff --git a/src/cli/actions/defaultAction.ts b/src/cli/actions/defaultAction.ts
index 3cadb9b11..40958563f 100644
--- a/src/cli/actions/defaultAction.ts
+++ b/src/cli/actions/defaultAction.ts
@@ -13,6 +13,7 @@ import { generateDefaultSkillName } from '../../core/skill/skillUtils.js';
 import { RepomixError, rethrowValidationErrorIfZodError } from '../../shared/errorHandle.js';
 import { logger } from '../../shared/logger.js';
 import { splitPatterns } from '../../shared/patternUtils.js';
+import type { RepomixProgressCallback } from '../../shared/types.js';
 import { reportResults } from '../cliReport.js';
 import { Spinner } from '../cliSpinner.js';
 import { promptSkillLocation, resolveAndPrepareSkillDir } from '../prompts/skillPrompts.js';
@@ -28,6 +29,7 @@ export const runDefaultAction = async (
   directories: string[],
   cwd: string,
   cliOptions: CliOptions,
+  progressCallback?: RepomixProgressCallback,
 ): Promise<DefaultActionRunnerResult> => {
   logger.trace('Loaded CLI options:', cliOptions);
 
@@ -113,16 +115,20 @@ export const runDefaultAction = async (
 
     const targetPaths = stdinFilePaths ? [cwd] : directories.map((directory) => path.resolve(cwd, directory));
 
-    packResult = await pack(
-      targetPaths,
-      config,
-      (message) => {
-        spinner.update(message);
-      },
-      {},
-      stdinFilePaths,
-      packOptions,
-    );
+    const handleProgress: RepomixProgressCallback = (message) => {
+      spinner.update(message);
+      if (progressCallback) {
+        try {
+          Promise.resolve(progressCallback(message)).catch((error) => {
+            logger.trace('progressCallback error:', error);
+          });
+        } catch (error) {
+          logger.trace('progressCallback error:', error);
+        }
+      }
+    };
+
+    packResult = await pack(targetPaths, config, handleProgress, {}, stdinFilePaths, packOptions);
 
     spinner.succeed('Packing completed successfully!');
   } catch (error) {
diff --git a/src/shared/types.ts b/src/shared/types.ts
index 6a30d6d9b..e0c49862b 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -1 +1 @@
-export type RepomixProgressCallback = (message: string) => void;
+export type RepomixProgressCallback = (message: string) => void | Promise<void>;
diff --git a/tests/cli/actions/defaultAction.test.ts b/tests/cli/actions/defaultAction.test.ts
index 920e94631..748993e39 100644
--- a/tests/cli/actions/defaultAction.test.ts
+++ b/tests/cli/actions/defaultAction.test.ts
@@ -6,6 +6,7 @@ import * as configLoader from '../../../src/config/configLoad.js';
 import * as fileStdin from '../../../src/core/file/fileStdin.js';
 import * as packageJsonParser from '../../../src/core/file/packageJsonParse.js';
 import * as packager from '../../../src/core/packager.js';
+import * as loggerModule from '../../../src/shared/logger.js';
 import { createMockConfig } from '../../testing/testUtils.js';
 
 vi.mock('../../../src/core/packager');
@@ -156,6 +157,95 @@ describe('defaultAction', () => {
     expect(mockSpinner.fail).toHaveBeenCalledWith('Error during packing');
   });
 
+  describe('progressCallback', () => {
+    it('should forward progress messages to the provided callback', async () => {
+      // Configure pack mock to invoke its 3rd argument (progressCallback)
+      vi.mocked(packager.pack).mockImplementation(async (_paths, _config, progressCallback = () => {}) => {
+        progressCallback('Searching for files...');
+        progressCallback('Processing files...');
+        return {
+          totalFiles: 10,
+          totalCharacters: 1000,
+          totalTokens: 200,
+          fileCharCounts: {},
+          fileTokenCounts: {},
+          suspiciousFilesResults: [],
+          suspiciousGitDiffResults: [],
+          suspiciousGitLogResults: [],
+          processedFiles: [],
+          safeFilePaths: [],
+          gitDiffTokenCount: 0,
+          gitLogTokenCount: 0,
+          skippedFiles: [],
+        };
+      });
+
+      const callback = vi.fn();
+      await runDefaultAction(['.'], process.cwd(), {}, callback);
+
+      expect(callback).toHaveBeenCalledWith('Searching for files...');
+      expect(callback).toHaveBeenCalledWith('Processing files...');
+    });
+
+    it('should isolate async callback errors without affecting pack flow', async () => {
+      vi.mocked(packager.pack).mockImplementation(async (_paths, _config, progressCallback = () => {}) => {
+        progressCallback('test message');
+        // Allow microtask to process the rejected promise
+        await new Promise((resolve) => setTimeout(resolve, 10));
+        return {
+          totalFiles: 10,
+          totalCharacters: 1000,
+          totalTokens: 200,
+          fileCharCounts: {},
+          fileTokenCounts: {},
+          suspiciousFilesResults: [],
+          suspiciousGitDiffResults: [],
+          suspiciousGitLogResults: [],
+          processedFiles: [],
+          safeFilePaths: [],
+          gitDiffTokenCount: 0,
+          gitLogTokenCount: 0,
+          skippedFiles: [],
+        };
+      });
+
+      const rejectingCallback = vi.fn().mockRejectedValue(new Error('callback error'));
+      const result = await runDefaultAction(['.'], process.cwd(), {}, rejectingCallback);
+
+      expect(result.packResult.totalFiles).toBe(10);
+      expect(loggerModule.logger.trace).toHaveBeenCalledWith('progressCallback error:', expect.any(Error));
+    });
+
+    it('should still update spinner even when callback throws synchronously', async () => {
+      vi.mocked(packager.pack).mockImplementation(async (_paths, _config, progressCallback = () => {}) => {
+        progressCallback('test message');
+        return {
+          totalFiles: 10,
+          totalCharacters: 1000,
+          totalTokens: 200,
+          fileCharCounts: {},
+          fileTokenCounts: {},
+          suspiciousFilesResults: [],
+          suspiciousGitDiffResults: [],
+          suspiciousGitLogResults: [],
+          processedFiles: [],
+          safeFilePaths: [],
+          gitDiffTokenCount: 0,
+          gitLogTokenCount: 0,
+          skippedFiles: [],
+        };
+      });
+
+      const throwingCallback = vi.fn().mockImplementation(() => {
+        throw new Error('sync error');
+      });
+      await runDefaultAction(['.'], process.cwd(), {}, throwingCallback);
+
+      // Spinner should still be updated despite callback failure
+      expect(mockSpinner.update).toHaveBeenCalledWith('test message');
+    });
+  });
+
   describe('buildCliConfig', () => {
     it('should handle custom include patterns', () => {
       const options = {